1. Field of the Invention
The present invention relates generally to acoustic surface wave signal processors employing interacting acoustical means for processing electrical input signals and yielding modified electrical output signals and, more particularly, concerns multiple track acoustic surface wave filters in which a portion of the acoustic energy in adjacent resonant systems is transferred back and forth to form a coupled resonant system.
2.Description of the Prior Art
Prior art acoustic wave filter devices have been realized in several forms. Such devices have been constructed by forming a network of interconnected acoustic transmission lines having substantially parallel tracks on a surface wave substrate, each track being realized between pairs of distributed surface wave reflectors on the surface of a planar piezoelectric element. Standing waves are excited at or are removed from the network by inter-digital electrode devices. Standing waves are coupled between the various resonant tracks by distributed angled arrays of reflector elements and are otherwise confined within the tracks by other reflector arrays.
The prior art, such as the technical paper in the I.E.E.E. 1976 Ultrasonics Symposium Proceedings by R. L. Rosenberg and L. A. Coldren entitled "Reflection-Dependent Coupling Between Grating Resonators", also considers acoustic wave filter devices formed by resonators placed side-by-side and coupled so that power can flow from an input to an output transducer. The coupling is provided by arrays of conductors each aligned parallel to the inter digital fingers of the transducers.